Cast aluminum parts are widely used in the aerospace and automotive industries to reduce weight. The most common cast alloy used, Al—Si7-Mg has well established strength limits. At present, cast materials in A356.0, the most commonly used Al—Si7-Mg alloy can reliably guarantee Ultimate Tensile Strength of 290 MPa, Tensile Yield Strength of 220 MPa with elongations of 8% or greater. The typical tensile properties of Al—Si7-Mg type high-strength D357 alloy are Ultimate Tensile Strength of 350 MPa, Tensile Yield Strength of 280 MPa with elongations of 5% or greater. In order to obtain lighter weight parts, higher strength material is needed with established material properties for design.
A variety of aluminum alloys, mainly wrought alloys, exhibit higher strength. The challenge in casting of these alloys has been the tendency to form hot tears during solidification. Hot tears are macroscopic fissures in a casting as a result of stress and the associated strain, generated during cooling, at a temperature above the non-equilibrium solidus. In most cases, the castings cannot be salvaged for further processing because of the hot tears. These wrought alloys are not suitable for use as casting alloys. Therefore, it is preferred to have an alloy with mechanical properties close to or superior to those of high-strength wrought alloys and which also has good castability, corrosion resistance and other properties.